In many cases, various housings of, for example, automobile electrical components, electric toothbrushes, shavers, and outdoor lighting devices are provided with a ventilation hole for the purpose of, for example, preventing deformation and burst of the housings due to temperature difference between inside and outside of the housings. In the case where the housings are provided with a ventilation hole, ventilation members including various waterproof gas permeable membranes are used in order to prevent water and dust from entering into the housings (see Patent Literatures 1 to 3).
For example, Patent Literature 3 discloses a ventilation member fabricated by welding a gas permeable membrane to an approximately cylindrical body (support body) made of a thermoplastic elastomer so as to close one opening of a through hole of the approximately cylindrical body. This ventilation member is fixed to a housing of an electrical component by utilizing the elasticity of the thermoplastic elastomer. Such a ventilation member has excellent productivity because it is fabricated by welding a flat (sheet-like) gas permeable membrane to an elastic body.
Usually, the gas permeable membrane used in a ventilation member has a sheet-like shape. As shown in FIG. 14, a common ventilation member 300 is composed of a support body 301 that is an approximately cylindrical body, and a sheet-like gas permeable membrane 303 provided so as to close one opening of a through hole 302 of the support body 301. The gas permeable membrane 303 is welded to the support body 301 (a welding portion 304) to be joined to the support body 301.
However, in a ventilation member with such a structure, there is a limitation in increasing further the gas permeation quantity because the gas permeable membrane has a sheet-like shape. Moreover, in recent years, hybrid cars and electric automobiles have been used more widely. Ventilation members attached to battery boxes, electrical components, etc. of these automobiles are required to have a further increased permeation quantity.
In components and devices that need internal pressure adjustment, an attachment area in which a ventilation member is to be attached cannot be ensured sufficiently in some cases. Particularly, automobile lamps have a problem in that a lamp lens surface is fogged with water condensation. Thus, a ventilation member with a larger gas permeation quantity needs to be attached in order to evaporate the condensed water quickly. However, since the area in which the ventilation member can be attached is limited, there has been a limitation in achievable gas permeation quantity.